Following an application from AlzChem AG, submitted for authorisation of a health claim pursuant to Article 13(5) of Regulation (EC) No 1924/2006 via the Competent Authority of Austria, the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) was asked to deliver an opinion on the scientific substantiation of a health claim related to creatine in combination with resistance training and improvement in muscle strength. The Panel considers that the food constituent, creatine, which is the subject of the health claim, is sufficiently characterised. The Panel considers that improvement in muscle strength is a beneficial physiological effect. A total of 21 human intervention studies and two meta-analyses were provided by the applicant as being pertinent to the claim. The Panel considers that no conclusions can be drawn from 11 studies and the meta-analyses cannot be used for the scientific substantiation of the claim. In weighing the evidence the Panel took into account that, overall, the human intervention studies submitted provide evidence for an effect of creatine, consumed at doses of at least 3 g/day in combination with regular resistance training (three times per week for several weeks) of moderate intensity, on muscle strength in adults over the age of 55, while no such effect was observed when similar doses of creatine on a weekly basis were given on training days only (three times per week). The Panel also took into account the plausible mechanism by which daily consumption of creatine in combination with resistance training could improve muscle strength. On the basis of the data presented, the Panel concludes that a cause and effect relationship has been established between the consumption of creatine in combination with resistance training and improvement in muscle strength in adults over the age of 55.